This invention relates generally to stretch wrapping apparatus and, more particularly, to a method for automatically changing the rolls of stretchable film during continuous operation.
Since its development in the 1970""s stretched plastic film has been used to secure cartons and bags on pallets for shipment. Films are stretched in a carriage and wrapped around the stacked product on a pallet. Two basic designs of wrapping apparatus are in use. The pallet may be placed on a turntable and the stretchable film dispensed from a stationary roll dispenser (rotary arm wrapper). In the alternative, the load may be stationary and the film wrapped using a rotating film dispenser (rotary arm wrapper). Turntable stretch wrapping apparatus is suitable for small volume production whereas the rotary arm wrapper may be integrated into a conveyor system and is more suitable for high volume production.
Regardless of the design of a stretch wrap packaging machine it has heretofore been necessary to manually reload the film roll when the roll has been consumed or, in the off chance the film breaks during wrapping. In most applications a roll of film is consumed at intervals of two to three hours and someone must be designated to monitor the wrapping machine while being committed to other tasks. In an automated environment, the production line would become stopped until someone manually reloaded the film.
U.S. Pat. No. 6,082,081 to Mucha discloses a pre-stretched roller assembly of a clam shell-type design which opens about a hinge and facilitates the loading of a stretch film. This film stretching apparatus is the preferred carriage assembly for use in an automated system for loading replacement film rolls.
It is the first objective of this invention to provide a completely automated system for replacing rolls of stretch film used in a carriage assembly for stretch wrapping of product on pallet and other shipping forms.
It is a second objective of this invention to provide a means for automatically responding to broken or torn film during wrapping with minimal stoppage of production lines.
It is yet another objective of this invention to facilitate unmanned operation of a packaging line with minimal attention requirements from production workers.
These and other objectives of the invention are obtained by providing an automatic changer for a stretch film having a turntable, a plurality of film mandrels removably attached to the turntable, an elevator, a means for opening a film delivery system prestretch roller assembly, a means for engaging the film mandrels into the roller assembly, a means for anchoring the end of the film separate from the roller assembly, a means for anchoring one end of the film away from the mandrel to provide a stationary source and a means for moving the turntable toward and away from the prestretched roller assembly.